This invention relates to indicators for disinfection or sterilization solutions. More specifically, this invention relates to devices that will indicate that an article has resided in a solution for disinfection or sterilization for a sufficient amount of time to carry out the intended disinfection or sterilization.
Infection control has become a major issue in society today. People now seek assurance that materials they come into contact with have been properly handled so as not to spread disease. This is particularly the case for the health care industry, and specifically the dental care field.
A number of methods have been developed to sterilize or disinfect materials used in the health care profession. These methods include steam sterilization, exposure to ethylene oxide gas and cold sterilization by placing materials in a solution of a material such as glutaraldehyde, phenolics and the like. Cold sterilization is often the only method that may be used to sterilize certain sensitive materials that would be damaged by application of steam or ethylene oxide gas. Cold solution methods may also be the most cost effective technique in certain small business environments.
U.S. Pat. No. 5,254,473 to Patel discloses a xe2x80x9csolid statexe2x80x9d self-contained device for monitoring integral values of time and temperature of storage of perishables. The composition comprises a dispersion of either a binder comprising a reaction inert, neutral finely divided absorbent, in the presence of a reactant comprising a salt of an acid or an organic compound substituted by at least one moiety which, in ionic form, is an anion or a binder/reactant, comprising at least one solid organic polymer whose constituent units contain, as a covalent substituent, at least one moiety which, in ionic form, is an anion. The composition further comprises an indicator, at least one acid sensitive pH dye, and as an activator, at least one base. The reactants incorporated in this construction either do not react or react slowly in liquid (solution or molten) state see column 7, lines 35-38. The device is therefore prepared and then dried at the time when initiation of the controlled reaction that is intended to measure the time that a material associated with the device such as food is no longer useable. See column 8, lines 47-52.
U.S. Pat. No. 4,212,153 to Kydonieus et. al. discloses a self-contained laminated indicator which changes in the visually perceptable mode with the passage of time. This time indicator device comprises two layers, whereby the molecular migration of an agent in an interior layer to the outermost surface of the exterior layer causes a change which can be visibly perceived. Preferred embodiments include the migration of a dye or the migration of an acid or base wherein the outermost layer has the other member of the acidbase pair, and a pH indicator. These constructions are also in the solid state and they are intended to be adhered to dry surfaces as a laminate.
U.S. Pat. No. 5,133,087 to Machida et.al. discloses a laminate comprising an innerlayer containing an acid/base indicator and an imbervious outer layer containing no acid/base indicator, wherein the inner layer is capable of undergoing a color change upon its contact with an acid or an alkali. This laminate construction utilizes the inner layer to provide indication of breakage of the outer layer, which is intended to provide protection against harsh acid or alkali materials. Such laminer constructions are suitable in the preparation of working gloves, and the like. This construction does not provided time indication of exposure to alkali or acid materials, but rather provides an indication of accidental breach of the outer layer.
U.S. Pat. No. 4,328,182 to Blake discloses sterilization indicators containing amino acid(s) and a pH indicator. This combination of components provides an indicator that is sensitive to exposure to formaldehyde vapor. In this system, the amino acid reacts with formaldehyde to reduce the pH of the acid according to the Sorenson reaction. Column 2, lines 3-14. A protective coating may optionally be provided to protect the reactants from handling and dilution from steam. This protective coating may also introduce a time delay in color change of the pH indicator. Column 2, lines 36-40 and 53-54. The usefulness of this indicator system is limited to formaldehyde vapor sterilization techniques.
The present invention provides a device for indicating residence time in a liquid disinfection solution, the device comprising a visually observable detector of exposure of the device to said solution, said device being selected such that upon exposure of the device to said solution the detector visibly changes at a predetermined time interval.
This device for the first time provides a person responsible for performing disinfection or sterilization tasks with tangible evidence that an article has been placed in a liquid disinfection or sterilization solution for the prescribed time interval. It is now also possible for the end user or health professional to have an assurance that an article to be used may be safely handled because it has undergone a sterilization or disinfection process.